A print friendly PDF version is available from this Communicable Diseases Intelligence issue's table of contents.
IntroductionGastrointestinal and foodborne diseases are a major cause of illness in Australia, despite the often mild nature of symptoms. The exact burden of disease due to food is not easy to quantify, as there is a significant under-estimate in surveillance data and there are multiple modes of transmission for gastrointestinal disease. Surveillance data may be biased by different levels of reporting of gastrointestinal disease in different age groups, with children and the elderly more likely to be seen by a medical practitioner.
It is important to recognise that differences in laboratory testing practices and surveillance methods in States and Territories may account for the difference in observed notification rates. This is particularly true for diseases such as Shiga-toxin producing E. coli (SLTEC/VTEC), where laboratory diagnosis is difficult, and screening practices vary between laboratories and jurisdictions. States and Territories also have different reporting requirements for doctors and laboratories, which can make national comparison difficult. To overcome some of these difficulties, the CDNA agreed to standardise reportable conditions in each jurisdiction from 1 January 2001.
In January 1999, the NSW Health Department established sentinel surveillance for foodborne disease in the Hunter Public Health Unit. This program of work was modelled on the Centers for Disease Control and Prevention (CDC) FoodNet Active Surveillance Network. The Hunter Public Health Unit heightened surveillance within the region for diarrhoeal disease and syndromic illnesses associated with food. It also established case control studies for Salmonella and Campylobacter. This pilot program of enhanced surveillance has run for over 2 years, and was used as a model for an Australia-wide program of heightened surveillance - coined OzFoodNet, in 2000.
The major outbreaks of foodborne illness in 1999 were the nationwide outbreak of typhoid following a cruise in the Pacific, and an outbreak of Salmonella Typhimurium PT135a associated with orange juice in South Australia. The outbreak of typhoid required multi-state cooperation, as cases were reported to various State and Territory health departments. The CDNA collaborative investigation was lead by the Victorian Department of Human Services.
BotulismThere have been no cases of foodborne botulism reported to the NNDSS since the inception of the system in 1991. A single case of infant botulism was reported in 1998. There were no cases of botulism reported in 1999.
CampylobacteriosisThere were 12,643 cases of campylobacteriosis notified to the NNDSS with symptom onset in 1999 (Table 1), which was a decrease of 6 per cent from 13,282 cases notified in 1998. Campylobacter species are the most common cause of gastrointestinal disease notified to the NNDSS. Despite this there are very few outbreaks detected due to the lack of a robust typing method. The median age of cases in 1999 was 26 years (range 0-94 years) and 53.4 per cent of notified cases were male. The highest age-specific rate was 188.2 cases per 100,000 population in 0-4 year-old children (Figure 8). The highest notification rates were in South Australia (161.1 per 100,000 population) and the lowest rates were in Western Australia (76.0 per 100,000 population, Table 2). Analysis by Statistical Division showed the highest rates of Campylobacter occurred in Outer Adelaide (186 per 100,000 population), the Western District of Victoria (163 per 100,000 population) and Yorke and Lower North in South Australia (163 per 100,000 population) (Map 2). Reports of campylobacteriosis were greatest in Spring and Summer (Figure 9). Campylobacter infections were not specifically notifiable in New South Wales.
Figure 8. Notification rate for campylobacteriosis, Australia, 1999, by age and sex
Top of pageFigure 9. Notifications of campylobacteriosis, Australia, 1991 to 1999, by month of onset
Map 2. Campylobacteriosis notification rate by Statistical Division of residence, 1999
Hepatitis AThere were 1,557 cases of hepatitis A notified to NNDSS with symptom onset in 1999 (Table 1), which was a decrease of 38 per cent from 2,443 cases notified in 1998 (Table 3). Although a faecal-oral route through contaminated food or shellfish from contaminated waters commonly spreads hepatitis A, recent outbreaks in the USA and Europe have been associated with injecting drug users. Similarly, in Australia in 1999, there were reports of hepatitis A outbreaks among injecting drug users.27,28 The median age of cases reported to NNDSS in 1999 was 24 years (0-98 years) and 54.7 per cent of notified cases were male. The highest age-specific rates were in 5-9 year-old children (16.5 cases per 100,000 population), and among adults aged between 20-29 years (16.9 cases per 100,000 population, Figure 10). The highest notification rates were in the Northern Territory (46.1 per 100,000 population) and the lowest rates were in Tasmania (1.1 per 100,000 population, Map 3). Reports of hepatitis A were received throughout the year, but were greatest in the month February (Figure 11).
Figure 10. Notification rate for hepatitis A, Australia, 1999, by age and sex
Figure 11. Notifications of hepatitis A, Australia, 1991 to 1999, by month of onset
Map 3. Hepatitis A notification rate by Statistical Division of residence, 1999
Top of page
Hepatitis EHepatitis E virus is now recognized taxonomically as the type species of the genus 'Hepatitis E-like viruses'. Hepatitis E virus (HEV) exhibits similarity in structure and genome organisation with the caliciviruses, and low amino acid similarity with rubella virus and the alphaviruses of the family Togaviridae. It is unrelated to the other hepatitis viruses (A, B, C, D, and G). HEV is associated with sporadic cases of enterically transmitted acute hepatitis. HEV is considered to be endemic in tropical and subtropical regions of Asia, Africa, and Central America. Antibody prevalence suggests global distribution of strains of low pathogenicity. Antibodies to HEV or closely related viruses have been detected in primates and swine. Women in the third trimester of pregnancy are susceptible to fulminant hepatitis E disease that has a case fatality rate as high as 20 per cent.29 Outbreaks in South Asia among young adults in recent years pose a risk to Australian travellers to these regions. There were 2 cases of hepatitis E notified to NNDSS in 1999, one of which was a 19-year-old male from Victoria and the other a 38-year-old male from the Australian Capital Territory. Both cases had a history of overseas travel and in one case it appeared the infection was acquired in India.
ListeriosisListeriosis is a serious but relatively rare foodborne disease to which neonates, pregnant women, the immunocompromised and the elderly are particularly susceptible. Infection during pregnancy can be transmitted to the foetus. Infants may be stillborn, born with septicaemia or develop meningitis in the neonatal period. Clusters of cases of listeriosis have been noted in hospitals, nurseries and aged care facilities.29
The interpretation of State and Territory comparisons of listeriosis data is complicated by reporting practices. Some jurisdictions report both cases of maternal-foetal pairs while others report the pair as a single case.
There were 63 cases of listeriosis reported to NNDSS with onset of symptoms in 1999, which was similar to previous years (Table 1). The median age of cases in 1999 was 60 years (0-86 years) and 55.6 per cent of notified cases were female. The highest age-specific rate was 2.1 cases per 100,000 population in 80-84 year-old people (Figure 12). The highest notification rates were in Western Australia (0.6 cases per 100,000 population) and there were no cases reported from the Northern Territory or the Australian Capital Territory. There was no evidence of clustering of cases of listeriosis. Victoria reported that 5 cases occurred as maternal-foetal cases, from which there were only 2 live births.
Figure 12. Notification rate for listeriosis, Australia, 1999, by age and sex
Salmonellosis (excluding typhoid)There were 7,154 cases of salmonellosis (not elsewhere classified) reported to NNDSS with symptom onset in 1999, which was a decrease of 9.5 per cent from 7,489 cases reported in 1998. The median age of cases in 1999 was 11 years (range 0-97) and 50.7 per cent of notified cases were male. The highest age-specific rate was 220.7 cases per 100,000 population in 0-4 year-old children (Figure 13). The highest notification rates were in the Northern Territory (184.6 per 100,000 population) and the lowest rates were reported from the Australian Capital Territory (20.7 per 100,000 population). The Kimberly Statistical Division had in excess of 300 cases per 100,000 population, which was comparable to previous years (Map 4). Reports of salmonellosis were greatest in the months January to March (Figure 14).
Figure 13. Notification rate for salmonellosis, Australia, 1999, by age and sex
Figure 14. Notifications of salmonellosis, Australia, 1991 to 1999, by month of onset
Top of pageMap 4. Salmonellosis notification rate by Statistical Division of residence, 1999
In Australia during 1999, the National Enteric Pathogen Surveillance Scheme (NEPSS) recorded 7,179 cases of non-typhoidal salmonellosis, and 15 outbreaks involving more than 10 cases, and 15 clusters of less than 10 cases (NEPSS 1999 annual report). The largest of these was an outbreak of 501 cases of Salmonella Typhimurium 135a associated with commercial orange juice. This outbreak occurred predominantly in South Australia, but cases were identified in neighbouring States.30 A waterborne outbreak of S. Saintpaul was reported in March 1999 in 28 workers at a large construction site in Central Queensland.31
Salmonella Typhimurium was the most common serovar reported to NEPSS in 1999, with phage types 135, 135a and 9 being the most common. NEPSS recorded 201 cases of Salmonella Enteriditis phage type 4. In New South Wales, the Australian Capital Territory, Victoria and South Australia, there were a total of 88 cases of S. Enteriditis phage type 4. Of those cases where data on overseas travel was available, all had a history of recent overseas travel, and the majority had travelled to Indonesia.
ShigellosisThere were 547 cases of shigellosis reported to NNDSS with onset of symptoms in 1999, which was a 8 per cent decrease from 594 cases reported in 1998. The median age of cases in 1999 was 21 years (range 0-83 years) and 54.1 per cent of notified cases were female. The highest age-specific rate was 13.0 cases per 100,000 population in 0-4 year-old children (Figure 15). The highest notification rates were in the Northern Territory (57.5 per 100,000 population) and the lowest rates were reported from Tasmania (0.2 per 100,000 population). Shigellosis was not specifically notifiable from New South Wales. Cases were more commonly notified during the months of January to April (Figure 16).
Figure 15. Notification rate for shigellosis, Australia, 1999, by age and sex
Figure 16. Notifications of shigellosis, Australia, 1991 to 1999, by month of onset
A report of a Shigella sonnei outbreak in a long-term nursing centre was reported.32 Thirteen cases of multi-drug resistant S. sonnei were found among staff and patients and the isolates were genetically indistinguishable. It is probable that transmission was person-to-person and that breakdowns in the institutional infection control procedures were responsible.
Shiga-like toxin producing Escherichia coli/Verotoxigenic E. coliThere were 43 cases of Shiga-like toxin producing Escherichia coli/Verotoxigenic E. coli (SLTEC/VTEC) reported to NNDSS with symptom onset in 1999, which was a 207 per cent increase from 14 cases reported in 1998. It should be noted however, that SLTEC/VTEC only became notifiable in August 1998, which may account for some of the increase in 1999. South Australia reported 90.7 per cent of cases, which reflects this State's policy of screening for toxin genes in faecal specimens (by PCR), from all cases of bloody diarrhoea. The median age of cases in 1999 was 33 years (range 1-77 years) and 37.2 per cent of notified cases were male. The highest age-specific rates were 0.5 per 100,000 population in 5-9 year-old children, and 0.9 per 100,000 population in 75-79 year-old people. SLTEC/VTEC was not specifically notifiable from Queensland or Western Australia.
Top of page
Haemolytic uraemic syndromeInfections with SLTEC/VTEC have the potential to cause severe and life-threatening illness including haemolytic uraemic syndrome (HUS). HUS is generally diagnosed on the basis of microangiopathic haemolytic anaemia, acute renal impairment and thrombocytopaenia (reduced platelet counts). Children aged less than 5 years are at increased risk of HUS. In an outbreak of HUS associated with the consumption of mettwurst in South Australia in 1994/1995 there was one death and 18 children required dialysis.33
There were 24 cases of HUS notified to NNDSS with symptom onset in 1999 (Table 1). States and Territories made this condition nationally notifiable in August 1998. New South Wales reported 11 cases and Victoria reported 8 cases. In New South Wales, 5 of the cases of HUS were considered to be a cluster. All presented with bloody diarrhoea, but no cultures were positive for VTEC. A common food source, minced beef, was postulated as the source of bacterial infection, but not proven.34 In Victoria, 8 cases and 2 deaths were reported, however, they appeared to be sporadic cases.35
The median age of cases reported to NNDSS in 1999 was 4.5 years (range 0-70 years) and 54 per cent of notified cases were female. The highest age-specific rate was 0.9 cases per 100,000 population in 0-4 year-old children.
TyphoidMost cases of typhoid in Australia occur in travellers returning to Australia from typhoid endemic countries. There were 72 cases of typhoid with symptom onset in 1999, which was a 12.5 per cent increase from 63 cases reported in 1998. The median age of cases reported to NNDSS in 1999 was 25.5 years (range 1-78 years) and 41.7 per cent of notified cases were female. The highest age-specific rate was 1.1 cases per 100,000 population in 25-29 year-old people (Figure 17). The highest notification rates were in New South Wales (0.6 per 100,000 population).
Figure 17. Notification rate for typhoid, Australia, 1999, by age and sex
In June 1999, Australian health departments were notified of 12 cases of typhoid in people who had attended a Pacific Island cruise in May 1999 (Typhoid Epidemiology Working Group, unpublished report). The CDNA coordinated a national response to the outbreak. All 12 cases of typhoid had attended a tour on the Kokoda Trail in Papua New Guinea. Investigators found that typhoid illness in tour participants was associated with either contaminated coleslaw or drinking water. A mixed infection was suspected as 81 per cent of 159 tour participants experienced gastroenteritis following the tour.
YersiniosisThere were 143 cases of yersiniosis reported to NNDSS with dates of symptom onset in 1999, which was a 25 per cent decrease from 190 cases reported in 1998. The median age of cases in 1999 was 19 years (range 0-86 years) and 56.6 per cent of notified cases were male. The highest age-specific rates were 3.8 cases per 100,000 population in 0-4 year-old children, and 1.1 per 100,000 population in 20-24 year-old people (Figure 18). The highest notification rates were in Queensland (2.9 per 100,000 population) and South Australia (1.2 per 100,000 population). Yersiniosis was not specifically notifiable in New South Wales. Cases were more commonly notified during January to March (Figure 19).
Figure 18. Notification rate for yersiniosis, Australia, 1999, by age and sex
Figure 19. Notifications of yersiniosis, Australia, 1991 to 1999, by month of onset
This article was published in Communicable Diseases Intelligence Volume 25, No 4, November 2001.
This issue - Vol 25, No 4, November 2001
NNDSS 1999 Annual Report
- Abstract and Authors
- Lists - Tables, Figures, Maps
- Statistical divisions
- 1999 review, Introduction, Methods, Notes
- Other surveillance reports